A PCR testing requires nucleic acid isolation/purification. In this process the nucleic acid solids from the biological sample are magnetically captured and then suspended in elution buffer solution. The purified end product is then transferred in a multi-vessel thermal cycler for PCR testing. During the isolation/purification process the nucleic acid from the biological material is bound to magnetic particles. The process requires several wash cycles of magnetic particles wash where the wash solution is discarded after each wash cycle. The magnetic particles plus the nucleic acid complexes are then eluted with an aqueous buffer. The eluted solution is transferred to the PCR testing vessel.
Recovery of the washed magnetic particles can be accomplished by removing the wash liquid from the wash vessel, usually with an aspiration probe. If the aspiration probe is used for aspirating other wash liquids from other wash vessels there is a risk of carryover from one wash vessel to another, and possible attraction of such carryover material to the cleansed magnetic particles.
One way of dealing with the carryover problem is to change the aspiration probe each time that sample or other liquid ingredient is aspirated from a sample tube or other liquid holding vessel. The changing of probes every time an aspiration is performed can be an expensive and time-consuming process.
Another way of dealing with the carryover problem is to wash any residue off the probe after each aspiration, before introducing the same probe into another sample tube or liquid holding vessel. The wash process is also time consuming and expensive.
It is thus desirable to remove liquid from a sample tube or other vessel, without using an aspiration device that makes physical contact with the liquid in a liquid-holding vessel. It is also desirable to substantially eliminate the carryover that is attributable to use of a common aspiration probe in different sample tubes or liquid holding vessels.
Transfer of the diluted solution to the PCR testing vessel without carryover is an important feature of the present invention.
Corresponding reference numbers indicate corresponding parts throughout the several views of the drawings.